1. Technical Field
Illustrative embodiments described in this patent specification generally relate to an image forming apparatus including an image carrier, a charger that charges the image carrier, a developing device that develops a latent image formed on the image carrier with toner to form a toner image on the image carrier, a transfer device that transfers the toner image formed on the image carrier onto a recording medium, and a cleaning device that removes residual toner adhering to the image carrier after transfer of the toner image onto the recording medium. Further illustrative embodiments described in this patent specification generally relate to a process cartridge removably installable in the image forming apparatus.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction devices having two or more of copying, printing, and facsimile functions, typically form a toner image on a recording medium (e.g., a sheet of paper, and the like) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of an image carrier (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
In the image forming apparatuses, the photoconductor is generally charged by electric discharge from a scorotron charger or the like, and products such as ozone are generated as a result. The products generated by electric discharge from the scorotron charger (hereinafter referred to as discharge products) must be dissolved using a catalyst and the like. For example, a fan or a blower is widely used to generate a flow of air to dissolve the discharge products through a filter including the catalyst and to discharge the dissolved products from the image forming apparatuses.
However, increasing demand for greater compactness of the image forming apparatuses reduces installation space for each component within the image forming apparatuses, necessitating use of complex shapes for the components. Consequently, the discharge products generated by electric discharge from the scorotron charger or the like cannot be completely cleared away using the catalyst and fan or blower described above. As a result, the discharge products may remain attached to a unit storing the charger or a charging member within the image forming apparatuses. The discharge products adhering to the unit storing the charger or the like may drop onto the surface of the photoconductor while the flow of air is stopped when the image forming apparatuses are turned off, for example at night, causing image deterioration, white spots, and the like. Further, the discharge products are hygroscopic, and therefore tend to attach to the surface of the photoconductor under high- temperature and high-humidity conditions.
In order to solve the above-described problems, a variety of techniques has been proposed to remove the discharge products generated by the electric discharge from the charger.
For example, scrubbers that remove the discharge products adhering to the surface of the photoconductor have been additionally provided to the image forming apparatuses. However, adding the scrubbers requires additional installation space therefor within the image forming apparatuses, thus complicating component design and increasing costs. Further, the surface of the photoconductor may be abraded by operation of the scrubbers, possibly shortening product life of the photoconductor.
In another approach, Published Unexamined Japanese Patent Application No. H06-149129 (hereinafter referred to as JP-H06-149129-A) discloses a technique in which reversal fog development of developer is performed on the surface of a photoconductor by driving a charger and applying a bias to a developing device while the apparatus warms up to remove substances adhering to the surface of the photoconductor the using a cleaning device. However, application of the bias to the developing device may itself generate the discharge products, and moreover, reversal fog development consumes a large amount of toner.
In yet another approach, in JP-2002-174996-A a technique in which a developed toner layer formed on the surface of a photoconductor is stopped at a position opposite a charger while the photoconductor is not driven has been proposed to prevent adhesion of a discharge products to the surface of a photoconductor. However, although the developed toner layer is formed at the position opposite the charger as described above, operation intervals are not changed even when a degree of adhesion of the toner is different.
In JP-3985931-B, still yet another technique has been proposed in which a scrubber including a water-bearing elastic layer and a high-absorbency layer is provided in addition to a cleaning device. The scrubber contacts a photoconductor to remove discharge products. However, because the scrubber is additionally provided as described above, additional installation space for the scrubber is required within the image forming apparatus, with the attendant disadvantages described above.